I'm not sure what to call them, but anyone know of research on the effectiveness of including the ability to resize text onscreen via a buttons/toggle. I mean the "aA" button you still sometimes see ...

For certain special pages I want to put content all on one page.
Think of them as cheatsheets (or similar) the idea being is that users should benefit from seeing the whole page in one glance.
However ...

I asked how I can resize the browser window with JavaScript. Everybody told me not to do it. Why is this a bad practice?
I think sometimes it can be good. For example, I want to show users a tweeting ...